Aliakbarinodehi, N. | bioRxiv Science

bioRxiv2024

Time Resolved Inspection of Ionizable-Lipid Facilitated Lipid Nanoparticle Disintegration and Cargo Release at an Endosomal Membrane Mimic

This study investigates pH-triggered fusion dynamics of lipid nanoparticles (LNPs) with an endosomal membrane mimic, addressing mechanistic aspects of a crucial yet elusive process for effective mRNA delivery. Utilizing time-resolved total internal reflection fluorescence (TIRF) imaging, we observed a delayed onset of LNP fusion upon pH drop, lasting seconds to minutes depending on pH and LNP size. Once initiated, LNP fusion and cargo escape occurred rapidly within tens to hundreds of milliseconds. While LNP disintegration is observed to lead to release of a significant portion of mRNA into the acidic environment, some mRNA molecules remained mobile on the endosomal membrane mimic due to deprotonation-resistant complex salt formation. Comparison of the fusion efficiency of two LNP formulations correlated with protein translation in human primary cell transfection data, emphasizing the importance of biophysical investigations in understanding ionizable-lipid-containing LNP-assisted mRNA delivery mechanisms and providing insights for optimizing mRNA-LNP design for enhanced endosomal escape.

biophysics↗

bioRxiv2021

Time evolution of PEG-shedding and serum protein coronation determines the cell uptake kinetics and delivery of lipid nanoparticle formulated mRNA

Development of efficient lipid nanoparticle (LNP) vectors remains a major challenge towards broad clinical translation of RNA therapeutics. New lipids will be required, but also better understanding LNP interactions with the biological environment. Herein, we model protein corona formation on PEG-ylated DLin-MC3-DMA LNPs and identify time-dependent maturation steps that critically unlock their cellular uptake and mRNA delivery. Uptake requires active serum proteins and precedes after a significant ([~]2 hours) lag-time, which we show can be eliminated by pre-incubating LNPs for 3-4 hours in serum-containing media. This indicates an important role of protein corona maturation for the pharmacokinetic effects of these LNPs. We show, using single-nanoparticle imaging, NMR diffusometry, SANS, and proteomics, that the LNPs, upon serum exposure, undergo rapid PEG-shedding ([~]30 minutes), followed by a slower rearrangement of the adsorbed protein layer. The PEG-shedding coincides in time with high surface abundance of Apolipoprotein A-II, whereas the LNPs preferentially bind Apolipoprotein E when their maximum uptake-competent state is reached. Finally, we show that pre-incubation of the LNPs enables rapid uptake and allows pulse-chase video-microscopy colocalization experiments with sufficiently short pulse durations to gain improved mechanistic understanding of how intracellular trafficking events determine delivery efficacy, emphasizing early endosomes as important delivery-mediating compartments.

biophysics↗